1. Field of the Invention
The present invention relates to a manufacturing method for a battery having a non-aqueous electrolyte (non-aqueous secondary battery).
2. Description of Related Art
A non-aqueous secondary battery such as a lithium ion battery and the like has light weight and high energy density as compared with existing batteries, and therefore is preferably used as a high output power source for mounting on vehicles in recent years. In manufacturing such battery, in general, firstly an electrode body is formed using a positive electrode and a negative electrode, and a battery assembly is constructed using the electrode body and a non-aqueous, electrolyte. Further, after prescribed initial charge (conditioning) and aging in a high-temperature environment are carried out on the constructed battery assembly, a performance qualification (e.g., self-discharge inspection) is performed.
In the self-discharge inspection, the battery assembly whose state of charge (SOC) has been adjusted is left to stand for a certain period of time. It is determined whether a minute internal short circuit occurs in the battery assembly by measuring the voltage drop amount during the stand (self-discharge) of the battery assembly. However, for an aged battery assembly, sometimes even after the SOC is adjusted, the voltage may be unstable temporarily, and the voltage may continuously rise or fall (hereinafter, such period is sometimes simply referred to as “voltage unstable period”). Therefore, in order to making an accurate inspection (determination), it is necessary to wait until the voltage of the battery assembly becomes sufficiently stable. Therefore, in the above manufacturing method, generally the time spent on manufacturing (typically, in the early stage in the self-discharge inspection, i.e., during the voltage unstable period) is apt to get longer. As a technique for dealing with this problem, there may be mentioned, for example, Japanese Patent Application Publication No. 2012-084346 (JP 2012-084346 A). In JP 2012-084346 A, a battery after aging is kept in a high SOC state for 1 to 7 days and then is forcibly discharged so that the amount of voltage difference before and after the forcible discharge is within a prescribed range. It is also described that by doing so, the self-discharge inspection period (during which the voltage is unstable) can be shortened.